Changes in brain cortical activity measured by EEG are related to individual exercise preferences

Abstract

Exercise is well known to result in changes of brain cortical activity measured by EEG. The aim of this study was (1) to localise exercise induced changes in brain cortical activity using a distributed source localisation algorithm and (2) to show that the effects of exercise are linked to participants' physical exercise preferences.

Electrocortical activity (5 min) and metabolical parameters (heart rate, lactate, peak oxygen uptake) of eleven recreational runners were recorded before and after incremental treadmill, arm crank and bicycle ergometry. Electroencephalographic activity was localised using standardised low resolution brain electromagnetic tomography (sLORETA).

Results revealed an increase in frontal α activity immediately post exercise whereas increases after bike exercise were found to be localised in parietal regions. All three kinds of exercise resulted in an increase of β activity in Brodmann area 7. Fifteen and thirty minutes post exercise a specific activation pattern (decrease in frontal brain activity–increase in occipital regions) was noticeable for treadmill and bike but not arm crank exercise.

We conclude that specific brain activation patterns are linked to different kinds of exercise and participants' physical exercise preferences.

Introduction

In the last twenty years the promotion of exercise has become an important public health message. This can be attributed primarily to the impact of exercise on cardio-respiratory and metabolic parameters and their influence on physical health [1]. But apart from those peripheral changes recent evidence suggests that there is also a major influence of exercise on brain cortical function which seems to be connected to changes in cognitive performance, general arousal and well being [2], [3].

It is generally agreed that there are temporary changes in the EEGs α and β activities caused by exercise [4], [5]. These changes were first reported in the 1950s [6] and are considered to reflect a state of accumulated relaxation [4], [7], [8].

An important aspect when considering effects of exercise on brain cortical activity is to assign effects to specific brain regions. Recent publications have contributed to the hypothesis that especially α activity within frontal brain regions is affected by exercise [9], [10], [11], [12], [13]. Although promising a fundamental limitation of these approaches is linked to missing possibilities of brain imaging during and immediately after exercise. In the recent years standardised low resolution brain electromagnetic tomography (sLORETA) has become an accepted method to localise changes in brain cortical activity by analysing EEG derivations [14], [15], [16], [17] especially in experimental situations that do not allow to use standard brain imaging methods like magnetic resonance imaging (MRI) or positron emission tomography (PET) [13], [18]. sLORETA is a source localisation method relying on mathematical models of the bio-electrical generators and the volume conductors within which they lie. It is based on standardised EEG recordings, which are modeled to a probabilistic head model provided by the Montreal Neurological Institute (MNI). Active cortical regions are identified created by allocating the raw sLORETA values of individual voxels to their corresponding Brodmann areas (BA) or cerebral gyri on the basis of the coordinates of the digitized Talairach Atlas [19]. Apart from sLORETA there are similar approaches to overcome the inverse solution like BESA, ST-MAP, MUSIC and others. By comparing these methods it gets clear that each has its own specific advantages but sLORETA was shown to give the most satisfactory results [20].

Just recently we were able to show that major changes in brain cortical activity occurred when individuals were allowed to exercise at their preferred intensity rather than constricting their intensity by heart-rate limits [21]. This is in accordance with previous findings, linking relaxational effects of exercise to individuals' physical activity history and exercise preferences [8], [22]. Accordingly we hypothesized that changes in brain cortical activity are connected not only to preferred exercise intensities but also to participants' exercise history. Within this study we tested a group of regular runners with little or no preferences to bike or arm crank exercise (i.e. none of these participants ever used an arm crank before, none of them was a regular biker) on changes in brain cortical activity after treadmill, bike and arm crank ergometry. We hypothesized that previously reported changes in EEG α and β activities, which were linked to recreational processes (changes in frontal α activity [12] and overall β activity [23]) would be dominant after treadmill but not arm crank and bike exercise.